Sign frame



FIG. 1 is a front perspective view of a sign frame showing our new design;

FIG. 2 is a rear perspective view thereof;

FIG. 3 is a front view thereof;

FIG. 4 is a side view thereof; and,

FIG. 5 is a top view thereof.

The broken lines immediately adjacent the shaded areas represent the bounds of the claimed design while all other broken lines are directed to environment and are for illustrative purposes only. 

CLAIM The ornamental design for a sign frame, as shown and described. 